Labyrinthulomycota is a group of eukaryotic single-cell microorganisms widely distributed in the ocean, and is classified in stramenopile (Kingdom Chromista, Heterokontae) having flagella of unequal length. This organism is an oil-containing microorganism that accumulates therein C22 polyunsaturated fatty acid (PUFA) such as docosahexaenoic acid (DHA) known as a functional food ingredient, and has therefore received attention as a source of single cell oil. The single cell oils are lipids produced by microorganisms. Lipids produced by microorganisms include special one not contained in oil-containing plants and in animal fats and oils and one having different composition. Therefore, these lipids are expected to be applied as novel lipid resources to pharmaceutical drugs, functional foods, feed, and the like. Examples of characteristics of microorganism fats and oils include, in addition to its peculiarity different from animal and plant fats and oils as described above, high productivity resulting from rapid proliferation, and ease of breeding of microorganism strains suitable for specific fats and oils production. The oil-containing microorganisms include Mucor and Mortierella filamentous fungi as γ-linolenic acid (C18:3)-producing microorganisms as well as Mortierella filamentous fungi as arachidonic acid (C20:4)-producing microorganisms. The γ-linolenic acid production using the microorganisms has already been put in industrial use. Because C22 fatty acids such as DHA grow in demand by the discovery of a variety of its high physiological functions and one of microorganism species of Labyrinthulomycota has a characteristic of producing PUFA as well as carotenoids such as astaxanthin exhibiting similar high physiological functions, which is not seen in existing biological resources, the development of production systems of these functional lipids using Labyrinthulomycota and systems effectively using the functional lipids as microorganism feed has been demanded. However, production mechanisms of PUFA and carotenoid, which are key factors in the development of the production system such as the optimization of culture conditions or molecular breeding, remain unexplained. Particularly, synthetic pathways of DHA in microorganisms of Labyrinthulomycota have not been elucidated.
In Japanese Patent No. 2764572, Japanese Patent Publication (Kokai) No. 2003-189846A (2003), and Molecular Biology of the Gene, Watson et al., Chapter 19, p. 595-620, Toppan, microorganisms known to accumulate polyunsaturated fatty acid including docosahexaenoic acid and other unsaturated fatty acids or carotenoid in the bodies have been explored diligently, and Labyrinthulomycota with high productivity has been found from among a number of microorganism groups. However, the productivity of polyunsaturated fatty acid and carotenoid by these microorganisms of Labyrinthulomycota disclosed therein is less than sufficient.